Fig. 3
The correlation between 40Ar/36Ar and 39Ar/36Ar. Measured 40Ar/36Ar and 39Ar/36Ar for eleven plagioclase-rich lithic fragments separated from 78461 trench regolith sample. Plagioclase-rich lithic fragments show linear fit with a slope of ~335. The 40Ar/39Ar age estimated based on 40Ar/39Ar = 335.44 is 4.33 ± 0.09 Ga. The dashed lines show 2σ deviations for the linear regression. (40Ar/36Ar)m and (39Ar/36Ar)m ratio were determined after correcting measured abundances of 36Ar, 40Ar, and 39Ar for blank contribution. In addition, the abundance of 36Ar was corrected for mass discrimination, and the abundance of 39Ar was corrected for radioactive decay since the time of sample irradiation. The numbers beside the symbols represent the sample names (e.g., 10 represents sample Plag#10)